This invention relates to pigmented thermoplastic resins. More particularly, this invention relates to pigmented polyester and/or polycarbonate resins wherein the multi-stage polymer compounded therewith provides impact resistance while improving depth of color and substantially eliminating non-uniform color appearance when the compounded pigmented polymer is molded into an article.
The impact strength of polyesters and/or polycarbonates is improved by compounding the resin with an impact modifier. However, when said compounded pigmented polyester or polycarbonate resin is molded into an article, the improvement of the impact strength is accomplished at the cost of the molded article having a non-uniform color appearance. This is often manifested by a whitesh or washed out non-uniform mother of pearl appearance (pearlescence), particularly in the area of the article which is nearest the gate or gates of the mold. Further, the visual appearance of the intensity of the color itself in the molded article also suffered and the molded article was not as pleasing to the consumer.
U.S. Pat. No. 3,971,835 is directed to an impact modifier-vinyl halide polymer composition. The impact polymer which comprises a hard first stage polymer which may be styrenic material and which may have up to 50 weight percent of a monovinylidene monomer interpolymerizable therewith. Additionally, a crosslinking agent may also be present in the first stage. The second stage is a rubbery polymer which may be a crosslinked alkyl acrylate, such as butyl acrylate. The final stage is a rigid thermoplastic polymer such as methyl methacrylate. U.S. Pat. No. 3,971,835 also teaches that pigments may be incorporated in the modifier-vinyl halide polymer system. The '835 patent does not address itself to the problem of non-uniform color appearance such as pearlescence in the molded article and further does not address itself to the problem of the intensity of color. The '835 patent deals with the problem of improving the impact resistance and clarity of a vinyl halide polymer composition.
U.S. Pat. No. 3,793,402 deals with the problem of haze level of an alkyl methacrylate polymer. The '402 patent provides an impact modifier which may have a crosslinked styrene core, an elastomeric stage and a final hard stage. The elastomeric stage may be a material such as a crosslinked alkyl acrylate and the outer stage may be an alkyl methacrylate such as methyl methacrylate. The '402 patent teaches that coloring materials may be present as part of the composition. U.S. Pat. No. 3,793,402 does not deal with the problem of pearlescence or intensity of color of a pigmented polyester and/or polycarbonate resin.
U.S. Pat. No. 3,162,695 deals with the problem of the flow characteristics of polycarbonate resins. The '695 patent is directed to a two stage graft copolymer having a core of a copolymer of butadiene and styrene and a shell of methyl methacrylate. The '695 patent does not teach the use of a pigment or coloring agent with the polycarbonate. Additionally, because butadiene is a necessary component of the polymer blend, the weatherability of the polycarbonate will be adversely affected because of the presence of butadiene in the core.
U.S. Pat. No. 3,864,428 is directed to a polyester/polycarbonate blend wherein there is present a graft copolymer of a butadiene polymer and a vinyl monomer. The vinyl monomer may be styrene. The butadiene-styrene copolymer is not crosslinked. The composition may have a coloring agent. The problem which was dealt with by the '428 patent was the problem of impact strength along with shapeability and resistance to thermal deformation and good chemical resistance. The '428 patent does not deal with the problem of pearlescence or intensity of color.
U.S. Pat. No. 3,891,719 is directed to a molding composition of a polycarbonate and a graft copolymer of styrene and acrylonitrile or an acrylic ester polymer. The problem which is dealt with by the '719 patent is the tensile strength, elongation and resistance to light and weather. This patent teaches that small amounts of butadiene-containing polymers cause changes in color under the effect of intense light and/or heat. The '719 patent teaches that pigments may be present in the thermoplastic molding composition. The graft polymers which are used in the '719 patent are all soft core containing materials such as butyl acrylate. The '719 patent does not recognize and does not deal with the problem of pearlescence and intensity of color.
U.S. Pat. No. 4,026,970 is directed to a non-pigmented polymer blend wherein a multi-stage polymer serves as a toughener for a thermoplastic resin such as a polyester or a polycarbonate. The core of the '970 multi-stage polymer contains a majority of acrylonitrile and a vinylidene monomer and a graftlinker. The vinylidene monomer may be styrene or a styrenic material. The composition of the '970 patent is a non-pigmented composition and the multi-stage polymer of the '970 patent contains, in the core, less than 50% of a styrenic material. Among the graftlinkers which the '970 patent sets forth is divinyl benzene which is one of the crosslinkers which are used in the present invention. The '970 patent does not recognize or deal with the problem of pearlescence or intensity of color.
None of the patents discussed above recognized the problem of pearlescence and intensity of color of a pigmented polyester and/or polycarbonate resin.
It is an object of this invention therefore to provide a pigmented polyester and/or polycarbonate resin compounded with an impact modifier which, when molded into an article, has good intensity of color and is non-pearlescent.
Other objects and advantages will become apparent from the following more complete description and claims.